Why Are Passthrough Binary Images Processed Individually and the First Image Repeated?

Below is an explanation of the issue based on how n8n handles binary images with passthrough enabled.

What’s Happening

When the passthrough binary images option is enabled, n8n automatically converts binary image data into image type messages for the downstream node(s). As a result:

• Individual Processing: Each binary image is processed as its own separate item. That’s why when you have three images, the downstream Agent node is triggered three times—once per image.
• Repeated First Image: The repetition of the first image in all iterations can occur if the workflow configuration doesn’t merge multiple binary inputs into a single payload. Instead, n8n uses the first image’s data when executing each iteration.

Why This Differs from Your Expectation

You expected that all three images would be passed as one aggregated payload (so you could ask questions about all of them in one single prompt). However, with passthrough turned on the behavior is to split up the images into separate messages. This isn’t a bug but rather the current design of the passthrough binary images option: it automatically sends each image individually.

How to Address This

To achieve your goal of passing all images together in one prompt, consider these approaches:

• Turn Off Passthrough: Disable the passthrough binary images feature so that binary images aren’t automatically converted.
• Combine Images Manually: Use additional nodes (such as a Merge or Set node) to collect and combine the binary image data from the incoming items into a single message. You can then pass that aggregated data to the Agent node.

By handling the binary data manually, you can format your data to match your desired structure (all images together) rather than relying on the default one-by-one execution.

Summary

• The current passthrough behavior sends binary images one at a time, causing the Agent to run separately for each image.
• The repetition of the first image indicates that the workflow isn’t aggregating the binary data as expected.
• To pass all images with a single prompt, disable the binary images passthrough or use nodes to merge the data manually before sending it on to the Agent.

This explanation should help you adjust your workflow configuration to better suit your requirements.